Deteriorating system components exposed to UV light
Has anyone else had problems with UV lights, EAC's and the other "new" air cleaners deteriorating the hydrocarbon based components of their HVAC systems? I just had another customer show me a filter that looked like Swiss cheese after being exposed to a UV light. The UV light and the ozone will react with any plastic materials such as filters, pans, wire, mastic, flex duct, etc. I would like to know how widespread this problem is and what people are doing about it.
It is very wide spread because most UV light systems get installed in the WRONG part of the system.
It seems that in my area, no installers have the slightest clue where they go in the system.
Every one of them I have seen was installed in the return plenum before the filter, or in the supply plenum. UV lights do absolutely nothing good for a system in those location.
Salesmen love adding them to systems because they are high profit margin, but talk them up as doing something that the UV light has no hope of doing. UV lights will do almost nothing to stuff that is traveling in the air because the air moves to fast to allow enough exposure time.
The only place a UV light system can do anything positive for the system is if it is shining directly on the entering air side of the indoor coil, and is located within a foot or so of it.
If more government is the answer, then it's a really stupid question.
Well said. One of the benefits of using some of the Photocatalytic Oxidation (PCO) designs is that you aren't trying to treat the air stream with the UV light and the design is focused on illuminating the internal coated sections of the photocatalyst. It treats the conditioned space on a longer exposure basis. Of course, some designs do actually try to condition the air stream - requiring much higher energy consumption to try and "zap" the bad stuff. Problem is that the bad stuff might not be constant in the air stream, leading to an overload of the good stuff - which can be just as bad for the occupants!
A little vodka is ok, a liter can kill you if you drink it all at once!
Nice subject for a change and everyone is right on the money from what I have witnessed so far in a lab setting and in the field. Most HVAC manufactures have changed the formula of the plastics they use in current coil boxes in residential systems to compensate for the use of UVGI Lighting. For the old systems depending on the UV wattage the bulb produces it will break down the pans if it has a direct irradiation on the pan in 3 to 5 years.
In the returns after at least merv 10 filtration is the place in a system that the highest kill rates can be achieved for this reason. A low out put bulb is the most common bulb on the market. Its optimum working temp is around 80 degrees so if the same bulb is put in an air stream of 55 degrees is reduces the output of the bulb by almost 40%. As what Mark said the only place to install just UVGI alone is in the coil box after improved air filtration.
As far as filters being burned by the UVGI lighting there are benefits of illuminating the back of the filter in a controlled commercial setting for biologic protection but never in a residential unit the risks of someone being burnt by the lights are too high. This is why in our residential line we use polished aluminum shields to protect the filters and project 100% of the light to the PCOs.
From what I have seen from field installs a 36 watt UVGI light will burn through a filter in about 3 weeks if the light is left on with no air flow. The systems I have seen with constant air flow have gone over 120 days before the holes start in the filters, like a variable speed system chiller system with VAV boxes and such.
Field testing by us and other universities show in PCO technology the higher the temp and the higher the humidity the better the removal rate is. So yo need to keep this in mind when installing any ones PCO system.
I am a nut with aluminum tape I tell people if in doubt cover it with foil tape. The only other technology I have really witnessed a lot of damage was in a very large (unnamed casino) they were using a very large commercial EAC System and in the beginning they said the could see some improvement in the smoke particulate then after about a year they started getting dirt clods falling out of the supplies on to the slots. What had happened was the magnetized particulate was collecting in the supplies that was making it passed the Merv 6 pleated filters they were using in the HVAC and was sticking to the supply ducting. The dirt in the supplies got so thick in a years time the air flow was rolling it in to balls and pushing it out of the supplies. They are in the process of replacing those ducts right now. It was a mess. Nothing bets good filtration humidity control and proper fresh air and sometimes thats not enough then you supplement with UVGI or UVGI with a PCO. Depends on what you want to achieve in the treated environment.
I must be missing the most basic logic here. When I go look at your 'systems' on your web site I see what looks like UVGI lights sandwiched between two filters. How does the UVGI ever reach the coil from between the two filters? Are these units to go under a furnace? How would the UV light reach past the blower and furnace to ever see the coil?
CX the top side of a WO units is a pleated mesh screen than has the TIO2 on it. The bottom of the unit is a merv 12 4 inch filter.And one of our basic beliefs in the office is a properly maintained system is the best system in residential units. And if you have a clean evap and coil pan to start with and add our UV/PCO system the improved filtration and the combination of the UVGI and the PCO your coil box should stay clean and mold free. The last testing we did't with the Army was showing on old removel we were hitting in the range of 90% plus in a single pass at around 1800 CFM
We are developing a system that sets on top of the coil for some one. But we are still in the testing phases of it, and still looking at proto types.
Sometimes a picture is worth a thousand words. Two filters exposed to UV light for 3 months.
Originally Posted by breathe easy
thought you said they couldn't kill anything in th airstream? looks like they killed this filter!
Originally Posted by breathe easy
Thanks B.E. Immediately after seeing this, I called my brother (the one with 8 kids) and told him to get that box of Trojans away from EAC & UV equipped furnace.
i installed 1 in my last house in miami fla.
i put it above the a-coil in my twe 048 it worked like a
charm it did not ruin anything from exposure,
as previously stated if you install it properly they are
component safe, but i dont think it treated the passing air
it sure did keep the coil clean and no mold would grow in the drain pan!
Stamas and Midhvac
Two of the best posts I have seen. I read them an hour ago and am still laughing. (especially the Trojan alert)
AirMech, the picture was just to illustrate the potential problems. UV lights are here to stay. I agree - great to keep the coil clean. My point is that we need to be aware of the potential negative effects on the hydrocarbon based components of the HVAC system and guard against their deterioration. For example, was that pan plastic?
your right, i did learn something after reading these posts!
Originally Posted by breathe easy
Great, no mold on the coils. I guess that means that if you don't want mold in the ducts, you'll need to install UV lights througout the ducts!
You can always do what one of our local hospitals is doing:
Doesn't solve the moisture and particulate accumulation that contribute to mold growth, but sure makes some money for the HVAC contractor with the contract. Especially since the ducts will have mold later, and they can come back and do it again!
Most UV lights have very limited effectiveness, and a short life . . .
How are you disposing of them? You realize that they contain mercury and are considered hazardous waste, right?
Are you shipping them back to the manufacturer for recycling?